[Spatiotemporal Variations in Nutrient Loads in River-lake System of Changdang Lake Catchment in 2016-2017].

Eutrophication of shallow lakes in the middle and lower reaches of the Yangtze River has become an increasingly serious problem. In this study, we investigated the temporal and spatial variations in nutrient loads (nitrogen, N and phosphorus, P) in the Changdang Lake Catchment located to the northwest of Lake Taihu through field sampling and laboratory analysis in 2016-2017. The results show the severity of the N and P pollution in the Changdang Lake catchment. The mean river water concentrations of TN, NO3--N, NH4+-N, TP, Chla, and permanganate index are (3.70±0.76) mg ·L-1, (1.81±0.42) mg ·L-1, (1.03±0.61) mg ·L-1, (0.38±0.31) mg ·L-1, (25.74±37.00) µg ·L-1, and (6.35±0.81) mg ·L-1, respectively. N pollution in the river is more severe in winter and spring than in summer and autumn whereas P pollution in the river is worse in autumn and winter than in spring and summer. Spatially, the magnitude of river N and P pollution follows the order of northern > northwestern > southern > eastern part of the study area. The rivers are in a state of moderate to severe eutrophication. The mean lake water concentrations of TN, NO3--N, NH4+-N, TP, Chla, and permanganate index are (2.25±0.94) mg ·L-1, (0.98±0.47) mg ·L-1, (0.19±0.14) mg ·L-1, (0.11±0.03) mg ·L-1, (18.71±8.76) µg ·L-1, and (4.59±1.09) mg ·L-1, respectively. The water quality in Changdang Lake is categorized as worse than class Ⅲ for TN and TP concentrations, which show decreasing trends from the west to the east to the south of the lake. The lake is in a status of slight to moderate eutrophication. The lake water quality is affected by the combination of sewage discharge and non-point source pollutant losses. The inflow rivers including the Danjinlicao River, Tongji River, and Xuebu River are the dominant pollution sources for Changdang Lake. The Danjinlicao River transports 10-12 times the total N and P loads transported by Tongji and Xuebu rivers. Changes in land use and atmospheric deposition are the driving factors of the deterioration of water quality and eutrophication in the catchment.

[Distribution and Pollution Assessment of Nutrients in the Surface Sediments of a Macrophyte-Dominated Zone in Lake Taihu].

To clarify the spatial distribution and pollution status of nutrients in the surface sediments from a macrophyte-dominated zone in Lake Taihu, total nitrogen (TN), total phosphorus (TP), alkali nitrogen (AN), available phosphorus (AP), and organic matter (OM) were measured at 60 sampling sites in Xukou Bay. A pollution evaluation and source apportionment analysis of these nutrients was also carried out. The average contents of TN, TP, AN, AP, and OM in the surface sediments of Xukou Bay were 1027.5, 423.2, 46.4, 15.3, and 17096.6 mg·kg-1, respectively, with the OM content being significantly higher in the northeast zone than in other areas of the bay. The average value of STN and STP was 1.75 and 0.91, respectively, indicating that TN and TP represent moderate and mild levels of pollution, respectively. The average comprehensive pollution index (FF) was 1.57, indicated that the surface sediment was moderately polluted. The observed organic pollution index indicated that the surface sediments in Xukou Bay were generally clean. Based on C/N values, organic matter in the surface sediments is derived from the bio-deposition of non-fibrous plants and phytoplankton. Based on correlation analysis, OM and TN in the surface sediments of Xukou Bay are derived from the same source, while TP is derived from an alternative source.

[Spatial Distribution and Pollution Assessment of Heavy Metals in River Sediments from Lake Taihu Basin].

To clarify the pollution characteristics of heavy metals in the surface sediments of rivers in economically developed areas, analysis of the contents of eight heavy metals, assessment of ecological risks, and identification of the source of heavy metals in surface sediments from typical rivers of Lake Taihu Basin were carried out in this study. The results showed that the average contents of Zn, Cr, Ni, Cu, Pb, As, Cd, and Hg in the surface sediments of Lake Taihu Basin were 163.62, 102.46, 45.50, 44.71, 37.00, 13.34, 0.479, and 0.109 mg·kg-1, respectively. Except for Hg, the average contents of other 7 heavy metals were higher than their background values. The geo-accumulation index indicated that Pb, Ni, Zn, Cu, and Cd amount to a low pollution state. According to the pollution load index, Pb, Ni, Zn, and Cu represent a moderately polluted state, while Cd, Cr, and As a low degree pollution state. Based on the potential ecological risk index, Cd and Hg represent moderate potential ecological risk, and the others low potential ecological risk. Source identification of heavy metals by multivariate statistical analysis showed that Pb was largely from non-point pollutions; Cr, Ni, and Zn stemmed from electroplating, alloy manufacturing industries, and nature; Cu and As were mainly from pesticides and discharge of industrial wastewater; Cd was dominantly from smelting industry; and Hg was mainly derived from fossil fuel combustion and petroleum products.

[Biodegradation Coefficients of Typical Pollutants in the Plain Rivers Network].

Biodegradation is a significant part of pollutant integrated degradation, the process rate of which is represented by the biodegradation coefficient. To investigate the biodegradation law of typical pollutants in the plain rivers network located in the upstream of the Lake Taihu, experiments were conducted in site in September 2015, one order kinetics model was used to measure the biodegradation coefficients for permanganate index, ammonia, total nitrogen and total phosphorus, and influencing factors of the biodegradation coefficients were also analyzed. The results showed that the biodegradation coefficients for permanganate index, ammonia, total nitrogen and total phosphorus were 0.008 3-0.126 4 d⁻¹, 0.002 1-0.213 8 d⁻¹, 0.002 1-0.090 5 d⁻¹ and 0.011 0- 0.152 8 d⁻¹, respectively. The influencing factors of the biodegradation coefficients for permanganate index were permanganate index and pH; those for ammonia were ammonia concentration and pH; those for total nitrogen were inorganic nitrogen concentration, total dissolved solid concentration and nitrite concentration; and those for total phosphorus were background concentration and pH. The research results were of important guiding significance for pollutants removal and ecological restoration of the plain rivers network located in the unstream of the Lake Taihu.

[Responses of Physiological Indices of Typical Submerged Macrophytes to Water Quality in Taihu Lake].

It was well known that physiological indices of submerged macrophytes could reflect change of water quality. The correlation between physiological indices of submerged macrophytes and change of water quality was studied under the cooperation of in-situ monitoring and lab analysis, combined with measuring Chlorophyll and free proline (PRO) contents as well as peroxidase (POD) activities in the leaves of Potamogeton wrightii Morong and Potamogeton crispus L. under different water quality and nutrition status. The results showed: ①there were significant spatial differences among water factors and the comprehensive eutrophication index (TLI) of distribution areas of Potamogeton wrightii Morong and Potamogeton crispus L. Mesotrophic water was more suitable for the growth of Potamogeton wrightii Morong, while Potamogeton crispus L. grew well in eutrophic water. ②there were significant spatial differences among physiological indices of Potamogeton wrightii Morong and Potamogeton crispus L. in Taihu Lake. Besides, there were significant relationships between Chlorophyll contents, POD activities of two species and TLI. ③water transparency as well as nitrogen and phosphorus nutrition were important factors leading to changes in Chlorophyll contents and POD activities of Potamogeton wrightii Morong and Potamogeton crispus L.. The findings from this study indicate that physiological properties of Potamogeton wrightii Morong and Potamogeton crispus L. have a very close correlation with nutrition status and physiochemical properties of water.

[Black water bloom induced by different types of organic matters and forming mechanisms of major odorous compounds].

Self-made glass reactors were employed to study the occurrence of black water bloom induced by different types of organic matters, to clarify the precursor of volatile organic sulfur compounds (VOSCs), and then to preliminarily study its degradation mechanisms under laboratory-controlled conditions. Our research indicated that provided organic matrix were as high as 1.0 g x L(-1), all organic matters could blacken the lake water regardless of sulfur appearance or not. However, compared with sulfur-free compounds that took more than 13 d to blacken the water, sulfur containing materials could accelerate the occurrence of black color to 7-13 d and increase the water chromaticity to above 410 which causing offensive odor consisted chiefly of DMDS, DMTS and DMTeS. Based on the function of methionine on the production of VOSCs, methionine was identified to be the precursors of VOSCs. Methionine was readily broke down by sulfate-reducing bacteria (SRB) (also other bacteria) (at 95% with the duration of 35 d) to produce hydrogen sulfide, methanethiol, and dominantly dimethylpolysulfides such as DMDS, DMTS and DMTeS. And the occurrence of black color had been advanced from 13 d to 8 d. Methanogenic bacteria slightly inhibited the degradation of methionine and reduced the evolution of sulfide. Therefore, the addition of methanogenic bacteria inhibitor set the formation of black color ahead by 1 d. Methionine was also degraded by nonbiodegradation, but it was a secondary pathway and cannot completely degrade methionine to blacken the water.

[Ecological characteristics of macrobenthos communities in Chaohu basin in spring and their relationships with environmental factors].

By the method of field investigation in combining with cluster analysis, multi-dimensional scaling analysis and canonical correspondence analysis, and using the indices of Shannon, Pielou, and Margalef, this paper studied the community structure and biodiversity of macrobenthos in the Chaohu basin in spring, and their relationships with environmental factors. A total of 23 macrobenthos species were collected, among which, six species (26.1% of total) were annelids, eight species (34.8%) were arthropods, and nine species (39.1%) were mollusks. The dominant species were Limnodrilus hoffmeisteri, Branchiura sowerbyi, and Bellamya aeruginosa, and their distribution had obvious spatial heterogeneity. The upper reaches of the rivers inside and out of Chaohu Lake had the highest macrobenthos biodiversity, followed by the Chaohu Lake and its estuary, and the lower reaches of the rivers inside and out of Chaohu Lake. The spatial distribution of the macrobenthos was also affected by various environmental factors, among which, Chl a and NO3(-) were the main ones.

[Community structure of phytoplankton and its relationships with environmental factors in drinking water source of Jinshu Bay, Taihu Lake].

By using canonical correspondence analysis (CCA), this paper studied the community structure of phytoplankton and its relationships with environmental factors in the drinking water source of Jinshu Bay, Taihu Lake. A total of 7 phylum and 58 genera were identified, and the phytoplankton community was dominated by Cyanophyta, Bacillariophyta, and Chlorophyta. The quantity of phytoplankton was slightly higher in summer (250 x 10(4) ind x L(-1)) than in spring (238 x 10(4) ind x L(-1)), but the community structure differed obviously between the two seasons. In spring, Cyanophyta was the dominant phylum, and Anabaena was the dominant genus; in summer, Chlorophyta was the dominant phylum, with no dominant genus but abundant quantity of Merismopedia and Scenedesmus. Besides temperature, the main environmental factors affecting the distribution of phytoplankton in spring were ammonium-nitrogen, total phosphorus, total nitrogen, and phosphate, while those in summer were total nitrogen, ammonium-nitrogen, phosphate, suspended solids, macrophytes, total phosphorus, and transparency.

[Spatial distribution characteristics and ecological significance of alkaline phosphatase in water column of Taihu Lake].

Based on different ecological zone of Taihu Lake, alkaline phosphatase activity (APA), the kinetic parameters and the chemical parameters in water column from different zone of Taihu Lake were monitored, and the spatial distribution characteristics and the effects of environmental factors on the values of APA, Vmax and Km were studied. The results showed that the values of APA, Vmax and Km in water column from Taihu Lake had a spatial heterogeneous distribution. The spatial distribution characteristic of APA values was the same as that of Vmax, ones in water from different zones of Taihu Lake, namely, the maximal values of APA (9.43 +/- 5.30) nmol x (L x min)(-1) and Vmax (13.70 +/- 7.42) nmol x (L x min)(-1) occurred in water from estuary zone in western bank of Taihu Lake. The value distribution of APA and Vmax in other zone of Taihu Lake followed as: the central zone of Taihu Lake > the grass type zone of Taihu Lake > the Meiliang Bay zone of Taihu Lake > the Zhushan Bay zone of Taihu Lake > the Gonghu Bay zone of Taihu Lake. The value of Km from the grass type zone of Taihu Lake was the highest (20.50 +/- 11.30) micromol x L(-1) , and the one from estuary zone in western bank of Taihu Lake was the lowest (9.17 +/- 3.46) micromol x L(-1) The value of kinetic parameter Vmax was significantly positively correlated with the values of pH, total phosphorus (TP) and the chlorophyll a (Chla), with r(pH) = 0.6512** (p < 0.01), r(TP) = 0.4885** (p < 0.01) and r(Chla) = 0.7656** (p < 0.01), respectively. However, the effects of hydro-temperature, dissolved total phosphorus (DTP) and orthophosphorus (PO4(3-) -P) on Vmax values were negligible. There was no significant influence of the hydro-temperature, pH, DTP, PO4(3-)-P and Chla concentrations on the Km values, nevertheless significant negative relationship between the Km value and TP content was found with r = -0.3834* (p = 0.048).

[Effects of elevated CO2 concentration on the growth of submerged macrophyte Potamogeton malaianus in Taihu Lake].

An outdoor culture experiment was conducted to study the growth and nutrient contents of submerged macrophyte Potamogeton malaianus in Taihu Lake under different CO2 concentrations. As affected by elevated CO2 concentration (1000 micromol x mol(-1)), the biomass per plant increased by 44.3% (P < 0.01), but the shoot biomass decreased by 5.5% (P < 0.05). The N content in root and leaf decreased by 18.1% (P < 0.05) and 6.4% (P < 0.05), respectively, but that in stem was less affected (P > 0.05). The P content in root, shoot, and leaf increased by 22.2% (P < 0.05), 26.6% (P > 0.05) and 38.8% (P < 0.05) , soluble sugar content increased by 27.3%, 18.3% and 37.5% (P < 0.05), and total C content increased by 4.6%, 5.3% and 2.0%, respectively. Elevated CO2 concentration decreased the N and P concentrations in water body by 7.9% and 5.1% (P < 0.05), respectively, but had less effects on the N and P contents in sediment. It was suggested that elevated CO2 concentration had definite effects on the growth and habitat of submerged macrophytes.

[Spatial distribution characteristics and environmental effect of N and P in water body of Taihu Lake].

The characteristics of spatial distribution of nitrogen and phosphorus in water were studied. The results showed that concentrations of total nitrogen/phosphorus in water from Meiliang Bay, Zhusan Bay, Gonghu Bay, West and Central Taihu Lake were obviously higher than those from any other region of Taihu Lake. The spatial distribution of dissolved nitrogen/phosphorus and detritus nitrogen/phosphorus was consistent with that of total nitrogen/phosphorus. The concentrations of dissolved nitrogen and detritus nitrogen significantly correlated with those of total nitrogen with rDN = 0.8192 and rDeN = 0.6969, respectively; the concentrations of dissolved and detritus phosphorus in water also significantly correlated with that of total phosphorus with rDP = 0.7477 and rDeP = 0.9260, respectively. The discrepancy in spatial distribution of chlorophyll a (Chla) in water was distinctly obvious, the highest level appeared in West Taihu Lake (179.2 microg x L(-1) +/- 25.9 microg x L(-1)), and the lowest in East Taihu Lake (11.3 microg x L(-1) +/- 2.7 microg x L(-1)). There were significantly linear relationships between total nitrogen, detritus nitrogen, total phosphorus, dissolved phosphorus, detritus phosphorus, permanganate index, pH value and suspended solids and the content of Chla with rTN = 0.6622, rDeN = 0.8739, rTP = 0.8130, rDP = 0.4077 and rDeP = 0.8781, rCOD = 0.8689, rpH = 0.5173 and rSS = 0.5334, respectively; while dissolved nitrogen, electric conductivity and alkalinity did not affect Chla in water from Taihu Lake.

[Nitrate vertical transport and simulating model in saturated soils in typical region].

By simulating soil column in laboratory, the nitrate vertical transport characteristics in farmland soil in Fengqu region of Henan Province were studied. The results show that, under saturated soil condition, the different concentrations of nitrate (100 mg x L(-1) 200mg x L(-1)) had no obvious influence on the breakthrough curves (BTCs) of nitrate vertical transport. When the soil columns were eluted by nitrate solution containing co-existing cations (K+ and Ca2+), the BTCs of nitrate vertical transport in the topsoil(0 - 30cm) of yellow fluvo-aquic soil and aeolian sandy soil were very similar. However, the outflow time of nitrate in the middle and bottom soil layers in the yellow fluvo-aquic soil was significantly extended, when the soil columns were eluted by nitrate solution containing Ca2+. The longer the outflow time of nitrate transport out of soil column was, the evener and lower the peak of the BTCs was. The mathematical model, CXTFIT2.0, could be applied to accurately estimate nitrate leaching mass in the saturated soil with steady-state flow condition. The fitted BTCs were in good agreement with the observed BTCs, which had high correlative coefficients (0.8594 - 0.9978).

[Hysteretic characteristics of atrazine desorption from fluvo-aquic soil].

Kinetic batch experiments are carried out in order to investigate the effects of a wide range of atrazine initial concentrations and consecutive desorption time on the desorption characteristics of atrazine from fluvo-aquic soil. The results reveal that, atrazine concentrations in soil solution gradually decreased with desorption time increasing, whose relationship can be expressed with empirically exponential functions. After consecutive five steps (or 5 days), when atrazine initial concentrations increased from 50 microg x L(-1) to 2000 microg x L(-1), the average desorption percentages were 23.1%, 30.4%, 33.0%, 36.4% and 38.5%, respectively. The relationships between the amount of atrazine adsorbed by soil colloids and corresponding atrazine concentrations in soil solutions may be described through the traditional and time-dependent desorption isotherms. The obvious discrepancies in two families of both traditional and time-dependent desorption isotherms from adsorption isotherm, which retention time last for 168 hours before commencement of desorption, were indicative of hysteresis. Two sets of Freundlich parameters derived from both desorption isotherms can quantify the hysteresis between desorption and adsorption isotherms. However, hysteresis coefficient, omega, was applicable only for the traditional desorption isotherms, H and lamda applicable for both.